In addition to the international games, there should be 8 NFL games played in non-NFL cities in the United States every year, primarily in large college stadiums. For example, Ohio Stadium in Columbus, home of the national champions, can host a Bengals game and a Browns game in years the AFC teams have 9 home games and neither is scheduled to host a game overseas, tickets for which can either be sold separately or as a 2-game package. All the gameday traditions for Ohio State games would be carried over to the NFL games.
These are the stadiums I could see hosting home games for nearby NFL teams:
Alamodome (San Antonio, TX): Dallas, Houston
Arizona Stadium (Tucson, AZ): Arizona
Autzen Stadium (Eugene, OR): Seattle
Bagwell Field at Dowdy–Ficklen Stadium (Greenville, NC): Carolina
Beaver Stadium (College Township, PA): Philadelphia, Pittsburgh
Bill Snyder Family Football Stadium (Manhattan, KS): Kansas City
Bobby Bowden Field at Doak S. Campbell Stadium (Tallahassee, FL): Jacksonville
Boone Pickens Stadium (Stillwater, OK): Dallas
Camp Randall Stadium (Madison, WI): Green Bay
Camping World Stadium (Orlando, FL): Jacksonville, Miami, Tampa Bay
Carl Smith Center, Home of David A. Harrison III Field at Scott Stadium (Charlottesville, VA): Washington
Darrell K Royal–Texas Memorial Stadium (Austin, TX): Dallas, Houston
David Booth Kansas Memorial Stadium (Lawrence, KS): Kansas City
Davis Wade Stadium at Scott Field (Mississippi State, MS): New Orleans
Donald W. Reynolds Razorback Stadium, Frank Broyles Field (Fayetteville, AR): Kansas City
Faurot Field at Memorial Stadium (Columbia, MO): Kansas City
Frank Howard Field at Clemson Memorial Stadium (Clemson, SC): Carolina
Gaylord Family Oklahoma Memorial Stadium (Norman, OK): Dallas
Jack Trice Stadium (Ames, IA): Chicago, Kansas City, Minnesota
Jones AT&T Stadium (Lubbock, TX): Dallas, Houston
Kenan Stadium (Chapel Hill, NC): Carolina
Kroger Field at C.M. Newton Grounds (Lexington, KY): Cincinnati
Kyle Field (College Station, TX): Dallas, Houston
L&N Federal Credit Union Stadium (Louisville, KY): Cincinnati, Indianapolis, Tennessee
Lane Stadium/Worsham Field (Blacksburg, VA): Washington
LaVell Edwards Stadium (Provo, UT): Denver
Memorial Stadium (Bloomington, IN): Indianapolis
Memorial Stadium (Champaign, IL): Chicago
Memorial Stadium, Tom Osborne Field (Lincoln, NE): Kansas City
Michigan Stadium (Ann Arbor, MI): Detroit
Mountaineer Field at Milan Puskar Stadium (Morgantown, WV): Pittsburgh
Neyland Stadium (Knoxville, TN): Tennessee
Nile Kinnick Stadium (Iowa City, IA): Chicago, Kansas City, Minnesota
Notre Dame Stadium (Notre Dame, IN): Chicago, Indianapolis
Ohio Stadium (Columbus, OH): Cincinnati, Cleveland
Pat Dye Field at Jordan–Hare Stadium (Auburn, AL): Atlanta
Rice–Eccles Stadium (Salt Lake City, UT): Denver
Ross–Ade Stadium (West Lafayette, IN): Chicago, Indianapolis
Saban Field at Bryant–Denny Stadium (Tuscaloosa, AL): New Orleans
Sanford Stadium (Athens, GA): Atlanta
Simmons Bank Liberty Stadium (Memphis, TN): New Orleans, Tennessee
Spartan Stadium (East Lansing, MI): Detroit
Steve Spurrier-Florida Field at Ben Hill Griffin Stadium (Gainesville, FL): Tampa Bay
Tiger Stadium (Baton Rouge, LA): New Orleans
Vaught–Hemingway Stadium at Hollingsworth Field (University, MS): New Orleans
Wayne Day Family Field at Carter–Finley Stadium (Raleigh, NC): Carolina
Williams-Brice Stadium (Columbia, SC): Carolina
Additionally, the NFL should also stage games at venues in non-NFL metro areas which have a large capacity but are designed either for auto racing or horse racing (similar to the CFB Battle at Bristol), like the Bengals can host the Ravens at Churchill Downs in Louisville, which would bring Lamar Jackson back to the city where he starred in college.